File size of scanned slides

I recently scanned about 1500 slides that were my fathers. I used the jumbl22 scanner set to 14MP file size. Some of the images, but not all show the file size around around 30 to 50MP. Has anyone ever ran into  situation like this before? I am using PSE13. I would appreciate any ideas or suggestions that anyone may have. I have tried to save it at a lower resolution but the file size stays the same.

Thanks Pops